1. Field of the Invention
The present invention relates to a wireless communication system for a multi-hop connection, in which a signal is transmitted between a source station, a plurality of relay stations and a destination station, and to the source station, relay stations, destination station and a pilot signal, all of which are used therein.
2. Description of Related Art
As the wireless communication system, a system using a single-hop connection method is known. Specifically, in the single-hop connection method, a station to be a source of transmitting a signal (hereinafter referred to as a “source station”) establishes a wireless link directly to a station as a destination of the transmission (hereinafter referred to as a “destination station”), thus performing the transmission of the signal. In this single-hope connection method, if a maximum transmission power in the source station is prescribed, large propagation loss and interference noise power make it impossible to establish the wireless link between the source station and the destination station, thereby resulting in lowering of an area coverage.
To the above problem, there is a multi-hop connection method, in which a plurality of relay stations are provided between the source station and the destination station and the signal transmission is relayed by these relay stations. This multi-hop connection method has been applied to TDMA (Time Division Multiple Access) and CSMA (Carrier Sense Multiple Access), because the method is effective in the point of preventing the lowering of the area coverage and of reducing a transmission power.
In the TDMA and CSMA, when selecting an appropriate transmission path among a plurality of transmission paths between the source station and the destination station, criteria related to avoidance of a packet collision and to the reduction of the transmission power were used as main criteria.
However, when the multi-hop connection method is applied to CDMA (Code Division Multiple Access), it is conceivable that, compared to the TDMA and CSMA, new interference noise generated when the relay stations relay the signal is increased. Thus, it is concerned that the increased interference noise becomes a factor that lowers a system capacity.